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Message-ID: <20250529031650.63880-1-qinyuntan@linux.alibaba.com>
Date: Thu, 29 May 2025 11:16:49 +0800
From: Qinyun Tan <qinyuntan@...ux.alibaba.com>
To: Tony Luck <tony.luck@...el.com>
Cc: "H . Peter Anvin" <hpa@...or.com>,
linux-kernel@...r.kernel.org,
x86@...nel.org,
Reinette Chatre <reinette.chatre@...el.com>,
Qinyun Tan <qinyuntan@...ux.alibaba.com>
Subject: [PATCH V2 0/1] x86/resctrl: Remove unappropriate references to cacheinfo in the resctrl subsystem.
V2:
- Keep sanity checks in the __mon_event_count to ensure execution occurs
exclusively on CPUs sharing the same L3 cache cluster
- When reading the top level event, obtain a CPU within hdr.cpu_mask.
Then use the cacheinfo shared_cpu_map of this CPU instead of using
hdr.cpu_mask directly
- Adjust code formatting and commit log descriptions.
In the resctrl subsystem's Sub-NUMA Cluster (SNC) mode, the rdt_mon_domain
structure previously relies on the cacheinfo interface to store L3 cache
information (e.g., shared_cpu_map) for monitoring. However, this approach
introduces risks when CPUs go offline:
The ci field in rdt_mon_domain is initialized using the first online CPU
of a NUMA node. When this CPU goes offline, its shared_cpu_map is cleared
to contain only the offline CPU itself. Subsequently, attempting to read
counters via smp_call_on_cpu(offline_cpu) would fail, but returning zero
values for "top-level events" without error indication.
To resolve these issues:
1. Replace direct cacheinfo references in struct rdt_mon_domain and struct
rmid_read with the cacheinfo ID (a unique identifier for the L3 cache).
2. The hdr.cpu_mask maintained by resctrl constitutes a subset of
shared_cpu_map. When reading top-level events, we dynamically select a CPU
from hdr.cpu_mask and utilize its corresponding shared_cpu_map for resctrl
to determine valid CPUs for reading RMID counter via the MSR interface.
Qinyun Tan (1):
x86/resctrl: Remove unappropriate references to cacheinfo in the
resctrl subsystem.
arch/x86/kernel/cpu/resctrl/core.c | 6 ++++--
fs/resctrl/ctrlmondata.c | 13 +++++++++----
fs/resctrl/internal.h | 4 ++--
fs/resctrl/monitor.c | 6 ++++--
fs/resctrl/rdtgroup.c | 6 +++---
include/linux/resctrl.h | 4 ++--
6 files changed, 24 insertions(+), 15 deletions(-)
--
2.43.5
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